The purpose of this research grant is to provide methodology for the isolation of human pancreatic carboxypeptidase B and human blood carboxypeptidase N. The study will give information on the active centers of both enzymes by using reagents already developed for bovine pancreatic carboxypeptidase B, and will include an immunochemical study of both enzymes to determine the extent of structural homology. This information will help clarify the physiological importance of carboxypeptidase N as a kinase and anaphylatoxin inactivator in the blood of mammals.